![RECTIFIER
Rectifier is a device which converts alternating current
(a.c.) into direct current(d.c.). [not smooth d.c. but
pulsating d.c.]
Types Of Rectifier
1) Half Wave Rectifier
2) Full Wave Rectifier
3) Bridge Rectifier](https://image.slidesharecdn.com/unit-2-230419085507-32589847/85/unit-2-pdf-25-320.jpg)
unit-2.pdf
- 1. UNIT-2 SEMICONDUCTOR DIODES AND ITS APPLICATIONS .
- 2. INDEX Introduction 2.1 P-N junction diode 2.2 Bridge Rectifier 2.3 'T' and „π‟' Filter circuits 2.4 Zener diode, Zener diode as voltage regulator
- 3. INTRODUCTION • The branch of engineering which deals with current conduction through a vacuum or gas or semiconductor is known as electronics. • In Electronics-electron present in all material. • All the material are composed of very small particles called atom . an atom consists of a central nucleus of positive charge around which small negatively charged particles called electron revolve in different path or orbit.
- 4. ATOMIC STRUCTURE • Atomic structure explanation is given by neils bohr , in 1913.
- 5. ELECTRONIC MATERIALS • The goal of electronic materials is to generate and control the flow of an electrical current. • Electronic materials include: 1. Conductors: It has low resistance which allows electrical current flow easily. e.g. Copper, silver, gold, aluminum etc. 2. Insulators: It has high resistance which does not allow electrical current flow. e.g. Glass, ceramic, plastics, & wood etc. 3. Semiconductors: can allow or suppress electrical current flow.e.g. carbon, silicon, germanium etc.
- 6. SEMICONDUCTOR • Semiconductors are materials that essentially can be conditioned to act as good conductors, or good insulators, or any thing in between. • Common elements such as carbon, silicon, and germanium are semiconductors. • Silicon is the best and most widely used semiconductor. • Its resistivity or conductivity lies in between conductor and insulator.
- 7. CONDUCTOR ATOMIC STRUCTURE • The atomic structure of good conductors usually includes only one electron in their outer shell. It is called a valence electron. It is easily striped from the atom, producing current flow. Copper Atom • The maximum number of electrons in a particular orbit is fixed. It is given by 2n2 , where n is the number of the orbit. E.g. first orbit, the number of electron is 2(1)2 = 2
- 8. SEMICONDUCTOR VALENCE ORBIT • The main characteristic of a semiconductor element is that it has four electrons in its outer or valence orbit.
- 9. CRYSTAL LATTICE STRUCTURE(CRYSTALLINE STRUCTURE OF SEMICONDUCTOR) • The unique capability of semiconductor atoms is their ability to link together to form a physical structure called a crystal lattice. • The atoms link together with one another sharing their outer electrons. These links are called covalent bonds.
- 10. SEMICONDUCTORS CAN BE INSULATORS • If the material is pure semiconductor material like silicon, the crystal lattice structure forms an excellent insulator since all the atoms are bound to one another and are not free for current flow. • Good insulating semiconductor material is referred to as intrinsic. • Since the outer valence electrons of each atom are tightly bound together with one another, the electrons are difficult to dislodge for current flow. • Silicon in this form is a great insulator. • Semiconductor material is often used as an insulator.
- 11. DOPING • To make the semiconductor conduct electricity, other atoms called impurities must be added. • “Impurities” are different elements. • This process is called doping.
- 12. SEMICONDUCTORS CAN BE CONDUCTORS (N –TYPE SEMICONDUCTOR) • An impurity, or element like arsenic, has 5 valence electrons is called penta valent element . • Adding arsenic (doping) will allow four of the arsenic valence electrons to bond with the neighboring silicon atoms. • The one electron left over for each arsenic atom becomes available to conduct current flow.
- 13. SEMICONDUCTORS CAN BE CONDUCTORS (P –TYPE SEMICONDUCTOR) • You can also dope a semiconductor material with an atom such as boron that has only 3 valence electrons is called trivalent element . • The 3 electrons in the outer orbit do form covalent bonds with its neighboring semiconductor atoms as before. But one electron is missing from the bond. • This place where a fourth electron should be is referred to as a hole. • The hole assumes a positive charge so it can attract electrons from some other source. • Holes become a type of current carrier like the electron to support current flow.
- 15. TYPES OF SEMICONDUCTOR MATERIALS • The silicon doped with extra electrons is called an “N type” semiconductor. • “N” is for negative, which is the charge of an electron. • Silicon doped with material missing electrons that produce locations called holes is called “P type” semiconductor. • “P” is for positive, which is the charge of a hole.
- 16. 2.1 P-N JUNCTION DIODE • When a p-type semiconductor material is suitably joined to n-type semiconductor the contact surface is called a P-N junction. • The p-n junction is also called as semiconductor diode . • A diode is a simple electrical device that allows the flow of current only in one direction. So it can be said to act somewhat like a switch.
- 17. • It is derived from “di-ode ” which means a device having two electrodes. The symbol of a p-n junction diode is shown below in fig , the arrowhead points in the direction of conventional current flow.
- 18. WORKING PRINCIPLE OF DIODE • The left side material is a p-type semiconductor having –ve acceptor ions and positively charged holes. The right side material is n-type semiconductor having +ve donor ions and free electrons DIODE IN FORWARD BIAS DIODE IN REVERSE BIAS
- 19. WORKING PRINCIPLE OF DIODE • When the diode is forward biased, due to the negative terminal on the n-side, electrons from the n-side are pushed towards the p-region. • Similarly due to positive voltage on the p-side of the diode, Holes from the p-region are pushed towards n- side. • Due to this the electrons will start converting the positive ions in the p-region into neutral atoms and holes will start converting the negative ions in the n- region to neutral atoms. • Hence width of the depletion region starts reducing due to reduction in the barrier potential. So current to flow from anode to cathode.
- 20. WORKING PRINCIPLE OF DIODE • When the diode is reverse biased , the hole from the p-side will get attracted towards the negative terminal of the supply and electrons from the n-side are attracted towards the positive terminal. • Hence the process of widening of the depletion region takes place and hence more and more opposition to the flow of current takes place.
- 21. VOLT-AMP CHARACTERISTICS (V-I CHARACTERISTICS) R A V diode VF Knee voltage VR IR(μA) IF(mA) Break over Voltage V
- 22. VOLT-AMP CHARACTERISTICS (V-I CHARACTERISTICS) • The supply voltage V is a regulated power supply, the diode is forward biased in the circuit shown. The resistor R is a current limiting resistor. • The voltage across the diode is measured with the help of voltmeter and the current is recorded using an ammeter. • By varying the supply voltage different sets of voltage and currents are obtained. By plotting these values on a graph, the forward characteristics can be obtained. It can be noted from the graph the current remains zero till the diode voltage attains the barrier potential. • For silicon diode, the barrier potential is 0.7 V and for Germanium diode, it is 0.3 V. The barrier potential is also called as knee voltage or cur-in voltage.
- 23. VOLT-AMP CHARACTERISTICS (V-I CHARACTERISTICS) • Knee voltage: The forward voltage at which the current through the forward biased diode start to increase rapidly is known as the knee voltage. • In the reverse characteristic, reverse current is very small and independent of applied reverse voltage, if temperature is constant. • The current rises rapidly when the breakdown voltage is reached. The reverse current is limited by the current limiting resistor R.
- 24. VOLT-AMP CHARACTERISTICS (V-I CHARACTERISTICS) Breakdown voltage: The reverse voltage at which the junction breaks down and results in sudden increase in reverse current is known as the breakdown voltage. Application of PN junction diode • As low power and high power rectifier • As a switch • In clipping and clamping circuit • As detector in AM radio receiver • For protection of transistor
- 25. RECTIFIER Rectifier is a device which converts alternating current (a.c.) into direct current(d.c.). [not smooth d.c. but pulsating d.c.] Types Of Rectifier 1) Half Wave Rectifier 2) Full Wave Rectifier 3) Bridge Rectifier
- 26. HALF WAVE RECTIFIER • During each “positive” half cycle of the AC sine wave, the diode is forward biased as the anode is positive with respect to the cathode resulting in current flowing through the diode.
- 27. HALF WAVE RECTIFIER • so we get output during positive half cycle as shown in waveform. • During each “negative” half cycle of the AC sinusoidal input waveform, the diode is reverse biased as the anode is negative with respect to the cathode. Therefore, NO current flows through the diode or circuit. • So we cant get out put at resistor during negative half cycle is zero.
- 29. FULL WAVE RECTIFIER • In a Full Wave Rectifier circuit two diodes are now used, one for each half of the cycle. A multiple winding transformer is used whose secondary winding is split equally into two halves with a common centre tapped connection • The full wave rectifier circuit consists of two power diodes connected to a single load resistance (RL) with each diode taking it in turn to supply current to the load.
- 30. FULL WAVE RECTIFIER • When point A of the transformer is positive with respect to point C, diode D1 conducts in the forward direction as indicated by the arrows. • When point B is positive (in the negative half of the cycle) with respect to point C, diode D2 conducts in the forward direction and the current flowing through resistor R is in the same direction for both half-cycles.
- 31. FULL WAVE BRIDGE RECTIFIER 2.2 Bridge wave Rectifier
- 32. POSITIVE HALF-CYCLE • During the positive half cycle of the supply, diodes D1 and D2conduct in series while diodes D3 and D4 are reverse biased.
- 33. NEGATIVE HALF-CYCLE • During the negative half cycle of the supply, diodes D3 and D4 conduct in series, but diodes D1 andD2 switch “OFF” as they are now reverse biased.
- 34. APPLICATION OF RECTIFIER • Dc supply is needed for various stages of TV receiver. • Circuit of radio receiver operates on D.C. supply. • D.C. supply is required for electroplating process. • Electronic equipment like Audio generator, CRO , amplifier required D.C. supply for their operation. • It is required for battery charging.
- 35. FILTERS Filter is the devices which converts the pulsating DC in to pure DC or smooth DC..
- 36. Π FILTER 2.3 'T' and ‘π’' Filter circuits • In this type of filter circuit two capacitor and one inductor are used. • First shunt capacitor C is connected then series inductor and then another capacitor C is connected in parallel.
- 37. Π FILTER • Most of the a.c. component are bypassed to ground by shunt capacitor and d.c. component can not pass through it. a.c. component can not pass through the inductor are bypassed to ground by another capacitor C. • This type of filter is known as the Π type filter because the shape formed by the two capacitor and one inductor resembles to the Greek letter Π.
- 38. “ T ” FILTER • A second common filter configuration is called the " T " filter - again, because it is shaped like the letter T. Input from rectifier Output • In this type of filter circuit two inductor and one capacitor are used. • First series inductor L1 is connected then shunt capacitor and then another inductor L2 is connected. Pulsating d.c. Smooth d.c.
- 39. 2.4 ZENER DIODE, ZENER DIODE AS VOLTAGE REGULATOR • Zener Diode : Works in the break down region when subjected to reverse bias. • Large variation in current. Voltage almost constant. • Used for voltage regulation. Upper limit of current depends on the power dissipation rating of the device.
- 40. V-I CHARACTERISTICS OF ZENER DIODE
- 41. V-I CHARACTERISTICS OF ZENER DIODE • Zener diodes are manufactured to have a very low reverse bias breakdown voltage. Since the breakdown at the zener voltage is so sharp, these devices are often used in voltage regulators to provide precise voltage references. The actual zener voltage is device dependent. For example, you can buy a 6V zener diode.
- 42. ZENER DIODE APPLICATIONS(ZENER DIODE AS VOLAGE REGULATOR): • The basic function of zener diode is to maintain a specific voltage across its terminals within given limits of line or load change. Typically it is used for providing a stable reference voltage for use in power supplies and other equipment.
- 43. ZENER DIODE APPLICATIONS(ZENER DIODE AS VOLAGE REGULATOR): In this simple illustration of zener regulation circuit, the zener diode will “adjust” its impedance based on varying input voltages and loads (RL) to be able to maintain its designated zener voltage. Zener current will increase or decrease directly with voltage input changes. The zener current will increase or decrease inversely with varying loads. Again, the zener has a finite range of operation.
- 44. APPLICATIONS OF ZENER DIODE: • As voltage regulator • As reference voltage device • In constant current source with transistor • In over voltage protection • In clipping and clamping circuit.
- 45. ANY QUESTION ?
- 46. THANK YOU